Because them's the rules

'As part of a drawing project I had to draw a view from a window. Security allowed me to do this but I was not allowed to draw the wall. I decided to replace it with the lines to the outline of the wall, following the rules, but still getting the feel of looking out from a prison.'- Anon, HMP Kirklevington Grange.

From the 2016 Koestler Award scheme for art made in prisons and secure hospitals.